The exemplary embodiment relates to digital image processing. It finds particular application in connection with context dependent cropping of images for generation of thumbnail images.
Thumbnail images are widely used as means of conveying information, such as identifying a source image, a document containing the image, a set of images comprising the image, or the like. In the context of web browsing, for example, a user may review thumbnail images as a way to identify potentially relevant documents related to the subject matter shown in the thumbnail image. Thumbnails images are also incorporated into documents in place of an original image where space constraints do not permit an entire image to be included or where only a portion of the image is of interest.
A thumbnail image is derived from a source image by resizing and/or cropping the source image. Thumbnail images are typically about the same size as an individual's thumbnail, though the actual size of a thumbnail image can vary depending on the particular application for which it is being used. Automated techniques have been developed for identifying salient features of an image, such as faces. These features are then retained in the cropping and become the focus of the thumbnail image.
There are many instances, however, where the resulting thumbnail image may not provide useful information for the specific application in which it is being used. For example, a researcher who is web browsing to find photographs or other information about a famous building may be more interested in what is often in the background of a photograph. This region is likely to be excluded from the thumbnail in automated cropping techniques employing saliency maps or rendered indecipherable when the source image is resized by reducing its resolution.